In order to forecast the productivity of perforated horizontal well, this paper introduced a three radial flow model based on the model used by Joshi in the derivation of horizontal well productivity formula. On the basis of the proposed model, this thesis derived out the productivity formula of perforated horizontal well with the equivalent flow resistance method, when the damaged zone is penetrated or not respectively. The productivity formulas takes many influencing factors into consideration such as the perforation length,shot density, perforation diameter, phasing, the diameter and the pollution degree of the damaged zone, the thickness and compaction damage degree of the crushed zone, the length of horizontal well, making the flowing mechanism more suitable for the real reservoir condition. The sensitivity analysis of the parameters with respect to the derived formulas shows: the productivity of perforated horizontal well rises with the increment of perforation length, shot density, perforation diameter, phasing, and the length of the horizontal well, and decreases as the thickness and compaction damage degree of the crushed zone increases. And, it is sensitive to the length of the horizontal well, perforation length, shot density and compaction damage degree, and is insensitive to phasing, perforation diameter, and thickness of the crushed zone. The perforation parameters is more sensitive with respect to the productivity index when the damaged zone is not penetrated than that penetrated. We should give priority to the length of the horizontal well, perforation length, shot density, and avoid excessive high compaction damage degree during the engineering design.